Databases

Chapter 3Organizing Data and Information

Introduction

Database: an organized collection of data

Database management system (DBMS): group of programs to manage databaseManipulates databaseProvides an interface between database and

the user of the database and other application programs

Database administrator (DBA): skilled IS professional who directs all activities related to an organization’s database

The Hierarchy of Data

Bit (a binary digit): a circuit that is either on or off

Byte: eight bits Character: basic building

block of information Each byte represents a

character Can be an uppercase letter,

lowercase letter, numeric digit, or special symbol

Field: typically a name, number, or combination of characters that describes an aspect of a business object or activity

Record: a collection of related data fields

File: a collection of related records

Database: a collection of integrated and related files

Hierarchy of data: bits, characters, fields, records, files, and databases

The Hierarchy of Data

Figure 3.1: The Hierarchy of Data

Data Entities, Attributes, and KeysEntity: a generalized class of people, places, or

things (objects) for which data is collected, stored, and maintained

Attribute: characteristic of an entityData item: value of an attributeKey: field or set of fields in a record that is

used to identify the recordPrimary key: field or set of fields that uniquely

identifies the record

Data Entities, Attributes, and Keys

Figure 3.2: Keys and Attributes

The Database Approach

Traditional approach to database management: separate data files are created for each applicationResults in data redundancy (duplication)

Data redundancy conflicts with data integrity

Database approach to database management: pool of related data is shared by multiple applicationsSignificant advantages over traditional approach

The Database Approach

Figure 3.3: The Database Approach to Data Management

The Database Approach

The Database Approach

Table 3.2: Disadvantages of the Database Approach

Data Modeling and the Relational Database Model

When building a database, consider:Content: What data should be collected, at what

cost?

Access: What data should be provided to which users and when?

Logical structure: How should data be arranged to make sense to a given user?

Physical organization: Where should data be physically located?

Data Modeling

Building a database requires two types of designsLogical design

Abstract model of how data should be structured and arranged to meet an organization’s information needs

Physical designFine-tunes the logical database design for

performance and cost considerations

Data Modeling

Data model: a diagram of data entities and their relationships

Entity-relationship (ER) diagrams: data models that use basic graphical symbols to show the organization of and relationships between data

The Relational Database Model Relational model: all

data elements are placed in two-dimensional tables (relations), which are the logical equivalent of files

In the relational model Each row of a table

represents a data entity

Columns of the table represent attributes

Domain: the allowable values for data attributes

Manipulating Data

Figure 3.7: Linking Data Tables to Answer an Inquiry

Database Management Systems (DBMS)

Interface between:Database and application programs Database and the user

Creating and implementing the right database system ensures that the database will support both business activities and goals

DBMS: a group of programs used as an interface between a database and application programs or a database and the user

Overview of Database Types

Flat fileSimple database program whose records have no

relationship to one another

Single userOnly one person can use the database at a timeExamples: Access, FileMaker, and InfoPath

Multiple userAllows dozens or hundreds of people to access the

same database system at the same timeExamples: Oracle, Sybase, and IBM

Creating and Modifying the Database

Data definition language (DDL) Collection of

instructions/commands that define and describe data and data relationships in a database

Allows database creator to describe the data and the data relationships that are to be contained in the schema

Data dictionary: a detailed description of all the data used in the database

Storing and Retrieving Data When an application requests

data from the DBMS, the application follows a logical access path

When the DBMS goes to a storage device to retrieve the requested data, it follows a path to the physical location (physical access path) where the data is stored

Manipulating Data and Generating Reports

Query-By-Example (QBE): a visual approach to developing database queries or requests

Data manipulation language (DML): commands that manipulate the data in a database

Structured Query Language (SQL): ANSI standard query language for relational databases

Database programs can produce reports, documents, and other outputs

Database Administration

Database administrator (DBA): directs or performs all activities to maintain a database environmentDesigning, implementing, and maintaining

the database system and the DBMSEstablishing policies and proceduresEmployee training

Popular Database Management Systems

Popular DBMSs for end users: Microsoft Access and FileMaker Pro

Entire market includes databases by IBM, Oracle, and Microsoft

Examples of open-source database systems: PostgreSQL and MySQL

Many traditional database programs are now available on open-source operating systems

Selecting a Database Management System

Important characteristics of databases to considerSize of the databaseCost of the systemNumber of concurrent usersPerformanceAbility to be integrated with other systemsVendor considerations

Using Databases with Other Software

Database management systems are often used with other software packages or the Internet

A database management system can act as a front-end application or a back-end applicationFront-end application: interacts with users Back-end application: interacts with

applications

Linking Databases to the Internet

Linking databases to the Internet is important for many organizations and people

Semantic Web Developing a seamless integration of traditional databases with

the Internet

Allows people to access and manipulate a number of traditional databases at the same time through the Internet

Data Warehouses, Data Marts, and Data Mining

Data warehouse: collects

business information from

many sources in the

enterprise

Data mart: a subset of a data

warehouse

Data mining: an information-

analysis tool for discovering

patterns and relationships in a

data warehouse or a data mart

Data Warehouses, Data Marts, and Data Mining

Table 3.5: Common Data-Mining Applications

Business Intelligence

Business intelligence (BI): gathering the right information in a timely manner and usable form and analyzing it to have a positive impact on business Turns data into useful

information that is then distributed throughout an enterprise

Competitive intelligence: aspect of business intelligence limited to information about competitors and the ways that knowledge affects strategy, tactics, and operations

Counterintelligence: steps an organization takes to protect information sought by “hostile” intelligence gatherers

Distributed Databases

Distributed databaseData may be spread across several smaller

databases connected via telecommunications devices

Corporations get more flexibility in how databases are organized and used

Replicated databaseHolds a duplicate set of frequently used data

Online Analytical Processing (OLAP)

Software that allows users to explore data from a number of different perspectives

Table 3.6: Comparison of OLAP and Data Mining

Object-Oriented and Object-Relational Database Management Systems

Object-oriented databaseStores both data and its processing

instructionsMethod: a procedure or actionMessage: a request to execute or run a

method

Visual, Audio, and Other Database Systems

Visual databases for storing images Audio databases for storing sound Virtual database systems: allow different databases

to work together as a unified database system Other special-purpose database systems

Spatial data technology: stores and accesses data according to the locations it describes and permits spatial queries and analysis

Video Clip

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